Nickel Based Superalloy Incoloy 800 (UNS N08800)
Nickel-Iron-Chromium alloy Incoloy 800 has fine strength and suitable resistance to
oxidation and carburization at high temperatures. It offers elevated temperature
performance in the petrochemical industry as it prevents the formation of embrittling sigma
phase subsequent to prolong use up to 1200oF or 649oC. Alloy 800 is used in the industrial
incinerators, heat processing equipments, chemical processing industries etc.
The compositional elements of Incoloy series are the refined elements that have established
industrial standards in the high temperature operations by offering suitable creeping and
rupturing characteristics. Incoloy 800 is a nickel- iron-chromium alloy with the supreme
resistance to corrosion. The resistance to heat and corrosion even with the limited nickel
concentration makes this alloy a strategic product.
Alloy 800 has been used in the extensive series of operations due to its vital resistance to
oxidation, carburization and other corrosions that occur in the elevated temperature
conditions. Its application series includes furnace operations and manufacturing
equipments, petrochemical furnace cracker vessels, pigtails and headers and shielding for
electrical heating elements.
Chemical Composition
The carbon content present in Incoloy 800 alloy is proportional to creeping and cracking
properties of alloy such that more carbon content, more are the creeping and cracking
properties. Therefore carbon is added significantly in the alloy on the base of special
application requirements. Carbon is added by 0.05% to 0.10% in the ASTM and ASME limits.
Aluminum (Al)
0.15 to 0.60 %
Carbon (C)
0.10 %
Chromium (Cr)
19 to 23 %
Copper (Cu)
0.75 %
Iron (Fe)
39.5 %
Manganese (Mn)
1.5 %
Nickel (Ni)
30 to 35 %
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Silicon (Si)
1%
Sulfur (S)
0.015 %
Titanium (Ti)
0.15 to 0.60 %
Physical Properties
Density
Ultimate tensile strength
Yield strength
Elongation %
Electrical resistivity
Magnetic Permeability
Curie temperature
Linear coefficient of thermal expansion
Specific heat capacity
Thermal conductivity
Melting point
Solidus point
Liquidus
7.94 gm per cubic cm or 0.287 lb per inch3
600 MPa or 87000 psi
500 MPa at 550oC or 72500 psi at 1020oF
275 Mpa or 39900 psi
213 Mop at 550oC or 30900 psi at 1020oF
45 %
35 % at 550oC or 1020oF
0.0000989 ohm-cm
1.014
-115oC or -175oF
14.4 micro-m/m-oC at 20oC to 100oC
8 micro-inch/inch-oF at 68oF to 212oF
0.460 J/goC or 0.110 BTU/lb-oF
11.5 W/m-K or 79.8 BTU-in/hr-ft2-oF
1357 to 1385oC or 2475 to 2525oF
1357oC or 2475oF
1385oC or 2525oF
Modulus of Elasticity
Temperature oF
-310 oF
75 oF
200 oF
400 oF
600 oF
Tensile Modulus, 10(3)ksi
30.55 x 10(3) ksi
28.50 x 10(3) ksi
27.82 x 10(3) ksi
26.81 x 10(3) ksi
25.71 x 10(3) ksi
Shear Modulus,10(3)ksi
11.45 x 10(3) ksi
10.64 x 10(3) ksi
10.37 x 10(3) ksi
9.91 x 10(3) ksi
9.47 x 10(3) ksi
Poisson’s Ratio
0.334
0.339
0.341
0.353
0.357
Electric & Thermal Properties
Temperature
Electrical Resistivity
Thermal Conductivity
Coef. Of Expansion
70 oF
20 oC
-
37 oC
-
200 oF
93 oC
80 Btu•in/ft(2)
in/in/°F
83 Btu•in/ft(2)
in/in/°F
89 Btu•in/ft(2)
in/in/°F
-
100 oF
595 ohm•circ
mil/ft
600 ohm•circ
mil/ft
620 ohm•circ
mil/ft
14.4
mm/m/oC
15.9
mm/m/oC
0.989 microohm.cm
1.035 microohm.cm
1.089 microohm.cm
11.5
W/moC
13
W/moC
14.7
W/moC
7.9 X 10(-6)
in/ in/ °F
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400 oF
204 oC
600 oF
315 oC
800 oF
426 oC
1000
oF
1200
oF
1400
oF
1600
oF
1800
oF
537 oC
2000
oF
1093 oC
648 oC
760 oC
871 oC
982 oC
657 ohm•circ
mil/ft
682 ohm•circ
mil/ft
704 ohm•circ
mil/ft
722 ohm•circ
mil/ft
746 ohm•circ
mil/ft
758 ohm•circ
mil/ft
770 ohm•circ
mil/ft
776 ohm•circ
mil/ft
1.127 microohm.cm
1.157 microohm.cm
1.191 microohm.cm
1.223 microohm.cm
1.251 microohm.cm
1.266 microohm.cm
1.283 microohm.cm
1.291 microohm.cm
788 ohm•circ mil/ft
103 Btu•in/ft(2)
in/in/°F
115 Btu•in/ft(2)
in/in/°F
127 Btu•in/ft(2)
in/in/°F
139 Btu•in/ft(2)
in/in/°F
152 Btu•in/ft(2)
in/in/°F
166 Btu•in/ft(2)
in/in/°F
181 Btu•in/ft(2)
in/in/°F
21.4
Btu•in/ft(2)
in/in/°F
-
16.3
W/moC
17.9
W/moC
19.5
W/moC
21.1
W/moC
22.8
W/moC
24.7
W/moC
27.1
W/moC
31.9
W/moC
8.8 X 10(-6)
in/ in/ °F
9.0 X 10(-6)
in/ in/ °F
9.2 X 10(-6)
in/ in/ °F
9.4 X 10(-6)
in/ in/ °F
9.6 X 10(-6)
in/ in/ °F
9.9 X 10(-6)
in/ in/ °F
10.2 X 10(6) in/ in/ °F
-
16.2
mm/m/oC
16.5
mm/m/oC
16.8
mm/m/oC
17.1
mm/m/oC
17.5
mm/m/oC
18
mm/m/oC
-
-
-
-
-
Mechanical Properties
The mechanical features of incoloy 800/800HT are paired with their resistance to corrosion
properties at the elevated temperatures that makes the Incoloy alloys extremely purposeful
for using in the different high temperature and long term oriented operations. These alloys
are also significantly used in the variety of corrosive media. The chemical composition limits
of Incoloy 800H and 800HT reside within the limits of INCOLOY alloy 800.
Alloy 800 comprises of large mechanical strength over high temperatures. It is suitable for
using up to 1500oF. The vital difference between Incoloy alloy series depends on the
difference of their mechanical properties. The difference in the mechanical properties is due
to difference in their chemical composition and the different temperature annealing.
Generally Incoloy 800 alloy possesses higher mechanical properties at the room
temperatures and minimum to high temperature exposures. On the other side the Incoloy
800H and 800HT alloys offer high creep and stress rupture strength at the higher
temperature exposures.
Tensile Properties
Incoloy 800 alloy offers high tensile features at the room and high temperatures. The tensile
characteristics at room temperature and 1200oF to 1800oF of extruded pipe and tubing are
described as following:
Temp.
Tensile
0.2% Yield Strength
1.0% Yield Strength
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Elongation
oC
RT
93 oC
100 oC
200 oC
204 oC
300 oC
316 oC
400 oC
538 oC
593 oC
600 oC
oF
RT
200 of
212 of
392 of
400 of
572 of
600 of
752 of
1000 of
1100 of
1112 of
Strength
N/mm2
500 N/mm2
<425> N/mm2
<400> N/mm2
<390> N/mm2
<360> N/mm2
<300> N/mm2
Ksi
72.5 Ksi
-
N/mm2
170 N/mm2
141 N/mm2
140 N/mm2
115 N/mm2
113 N/mm2
95 N/mm2
93 N/mm2
80 N/mm2
77 N/mm2
75 N/mm2
75 N/mm2
Ksi
24.7 Ksi
20.4 Ksi
20.3 Ksi
16.7 Ksi
16.4 Ksi
13.8 Ksi
13.5 Ksi
11.6 Ksi
11.2 Ksi
10.9 Ksi
10.9 Ksi
N/mm2
200 N/mm2
161 N/mm2
160 N/mm2
135 N/mm2
133 N/mm2
115 N/mm2
113 N/mm2
100 N/mm2
97 N/mm2
95 N/mm2
95 N/mm2
Ksi
29.0 Ksi
23.3 Ksi
23.2 Ksi
19.6 Ksi
19.3 Ksi
16.7 Ksi
16.4 Ksi
14.5 Ksi
14.1 Ksi
13.8 Ksi
13.8 Ksi
A5%
Transverse
30
Longitudinal
35
Corrosion Resistance
Incoloy 800 alloy offers excellent resistance to the chloride ion stress corrosion cracking and
embrittlement in precipitation sigma phase. It offers superior resistance to corrosion in the
different media. In the solution annealed form, it offers high creep stress rupturing features.
It can be sensitized to intergranular corrosion in the rigorous conditions.
In an analysis, alloy 800 is subjected to boiling nitric acid of 65% concentration for 5 hours
that determines alloy’s inclination to sensitization. When Incoloy 800 is set to heat from
welding or other processes, precautions should be made to prevent sensitization when it
needs to be pickled or kept in the various severe conditions. The sensitization of alloy is not
an issue in the various elevated temperature operations.
Incoloy 800H and 800HT offer extremely high creep and cracking strength properties as
compare to Incoloy 800. These alloys possess almost similar chemical composition such that
the content % of the basic elements like nickel, chromium and iron is same. But, the
composition varies in terms of concentration of carbon, titanium and aluminum. The
concentration of carbon in Incoloy 800 is 0.10%. Outstanding resistance to chloride ion
stress corrosion cracking, oxidation and carburization.
Average corrosion rate in a variety of corrosive media
Media
10% C2H4O2
5% Al2(SO4)3 • 18H2O
5% NH4Cl
10% NH4OH
5% (NH4)2 SO4
Test time
7 days
7 days
42 days
7 days
7 days
Corrosion rate, mpy
0.01 mpy
0.01 mpy
0.02 mpy
0.01 mpy
Nil
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10% BaCl2
5% CaCl2
5% H2CrO4
10% C6H8O7
10% CuSO4
5% FeCl3
10% C3H6O3
CH3OH
10% C2H2O4
5% C6N6FeK3
5% NaHSO3
20% Na2CO3
NaCl
5% NaOCl
5% Na2SO4
10% C4H6O6
10% ZnCl2
42 days
42 days
7 days
7 days
7 days
42 days
7 days
7 days
7 days
7 days
7 days
7 days
42 days
42 days
7 days
7 days
42 days
0.03 mpy
0.01 mpy
1.6 mpy
Nil
Nil
420 mpy
0.04 mpy
Nil
11 mpy
0.04 mpy
0.03 mpy
Nil
0.34 mpy
8 mpy
Nil
0.02 mpy
0.01 mpy
Fabrication
Different machined forms of Incoloy 800 are forged into the end products and equipments
by following the ordinary methods. Alloy 800 is readily forged by hot or cold processing and
it has superior welding and machining character.
Heating and Pickling
The heating specimen should be clean that whole oil, grease, dust and other unwanted
materials should be removed before beginning the heating process. Heating is preferred in
the nominal sulfur conditions. The open heating in the nominal sulfur content and furnace
conditions should be done in the reducing medium to avoid the extensive oxidation. Due to
eagerness of chromium to get oxidized in a refractory oxide or water, it is tough to bright
anneal the Incoloy 800 in the common commercial annealing furnace. In the limited
conditions, the Incoloy alloy can be bright annealed in arid, pure hydrogen atmosphere.
Incoloy 800 is annealed in the muffle furnaces by utilizing reducing media. The contended
atmosphere is produced by products of combustion from minor sulfur natural gas burnt
with minimum air. It creates thin, long standing and green black oxide layer on alloy. The
oxidizing media create heavy oxide scale that is tough to clean. Such type of cleaning needs
grinding to some extent. The certain annealing processes are based on the quantity of cold
processing of specimen.
The mechanical features of severely cold processed alloy are nominally influenced at
temperatures lower than 1000oF. The stress release starts from 1000oF and fulfills after 1.5
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hours at 1600oF. The softening of alloy is done by annealing up to 1400oF and is completed
after 10 – 15 minutes heating up to 1800oF.
The suitable grain growth starts at 1800oF. The suitable annealing can be done by heating
Incoloy 800 up to 1900oF for 2-5 minutes. The annealing temperature influences the grain
size and room temperature mechanical characteristics of alloy 800. The alloy material is held
at temperature for 15 minutes and air quenching is done prior to analysis. The oxide layer
and scale produced are cleaned through pickling process. As the Incoloy 800 resists the
chemical corrosion therefore specific pickling methods are followed.
Hot and cold Fabrication of Incoloy 800
The hot fabrication of Incoloy 800 is performed at temperatures from 1600oF to 2200oF.
The heavy forging is performed at 1850oF to 2200oF. The forging done at 1200oF to 1600oF
may cause cracking in the material. The quenching rate followed after hot forging is not
significant in correspondence to thermal cracking.
Incoloy 800 alloy is subjected to carbide precipitation at 1000oF to 1400oF and it should be
quenched quickly while preventing sensitization. The cold processing is performed by
following processes that are followed for processing of Inconel 600 and stainless steel
grades. The work toughening rate of Incoloy 800 is more than the mild steel rate however it
is lesser than steel 304. The work toughening rate of alloy 800 is almost similar with the
Inconel 600.
Machining of Incoloy 800
Incoloy 800 is readily machined by following the standard processes. The turning can be
done by large metal eradication rates, high apparatus service life and excellent surface finish
and by utilizing coated carbide equipments. The coated carbide equipments provide
enhanced service life at seizing rate of 110-190 sfpm and 0.20 to 0.89 mm per rev. The large
speed steel equipments provide extended life at the cutting speed of 35-95 sfpm and input
rate of 0.008 to 0.035 ipr.
Welding Features of Incoloy 800 alloy:
Incoloy 800 offers excellent welding character. It can be welded by whole welding methods.
The alloy that needs to be welded should be cleaned and accurate joined layouts should be
utilized. The Inco Weld A electrode is a preferred welding product that is used in the
shielded metal arc welding. Inconel filer metal 82 is used in gas tungsten arc welding
method. The incoflux 4 submerged arc flux is utilized in the submerged arc method. These
materials are utilized for unlike welding needs for Incoloy 800.
Available forms
Wire, mesh, strip, foil, bar, rod, pipe, tube, plate, sheet and flanges
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